Electrodeposition of metals



Patented Apr. 23, 1940 ELECTRODEPOSITION F METALS Rudolf Lind, Euclid,William J. Harshaw, Shaker Heights, and Kenneth E. Long, South Euclid,Ohio, assignors to The Harshaw Chemical Company, Elyria, Ohio, acorporation of Ohio No Drawing. Application December 14, 1939, SerialNo. 309,233

18 Claims. (01. 204-14) This invention relates as indicated toelectrodeposition of metals and more specifically to a process of andmaterials for use in the process of electrodepositing nickelcharacterized in that the nickel to be built up before the brightness ofthe base metal was materially diminished. When unpolished articles areplated in such baths, the deposit is not truly bright but merely, atbest, has

resultant nickel plate, as deposited, is both bright the same characteras the base metal. The 5 and ductile. More particularly, the presentinbrightness produced by such addition agents may, vention has to dowith new addition agents for therefore, be characterized as brightnessdiminproducing the above-named desirable characterishing with increasedthickness of plate on a istics in the nickel plate and which may be usedpolished surface.

with acid nickel baths of usual composition oper- Others of theseprevious nickel plating addi- 10 ating under usual conditions. tionagents have produced a plate which would In order to properly evaluatethe present inmaintain the brightness of the polished base vention, itis necessary to define brightness and surface, even though the plate wasbuilt up to a ductility or brittleness, terms used in the old art,substantial thickness. They would not build up but used loosely todescribe all degrees of brightany substantial brightness on anunpolished surness or brittleness. face and, at best, would only veryslowly build Brightness up brightness on an unpolished surface whenplates of extreme thickness were made. The It S Obv ous that an extre yt deposit of brightness produced by such addition agents may,

nickel v r a hi hly bufied surface will ppear therefore, becharacterized as brightness maln- 20 ri h Bright p a es of this typehave been made taining itself with increased thickness of plate foryears and are well recognized in the art. on a polished surface.

Their limitations are that if the plated article is The addition agentsof the present invenexposed to the atmosphere or to wear, the plate tionproduce a plate that not only maintains the soon disappears or wearsoff. A plate thin enough brightness of the most highly polished basemetal, 25 so that it will retain substantially the fullbrightirrespective of the thickness of the plate within n f h polishedbase metal i impr c i l for practical limits, but also increases inbrightness use even as a base for the electrodeposition therewithincrease in thickness of the plate on an unover of a protective coatingof other metals such polished surface. The brightness produced by aschromium. If a heavier deposit is plated out, such addition agents may,therefore, be charac- 30 the ri h ness of the i ly b fed surface (11-terized as brightness increasing with thickness minishes and a gray orwhite dull deposit is 0bof plate on an unpolished surface. tamed'Ductz'lit A nickel plate which is thick enough to be pracy tical for useand which is bright without bufllng is The question of ductility is oneof vital con- 5 not only desirable per se, but it is particularly adcernto the plater. In general, all bright plates vantageous where it isdestined for use as the are harder and, therefore, more brittle thanordibase for an electrolytically deposited chromium nary dull nickel.When enough of many of the plate, since, if the nickel plate does notrequire to p ev ously p yed dition agents was added 40 be polished andbuffed, a relatively thin plate to a bath to produce a bright plate, theplate was 40 gives the same protection as the necessarily often toobrittle for commercial use and yet if heavier gray plate, some of whichmust be taken less addition agent was used, the plate would not off inthe polishing to secure the desired brlghtbe fully bright. ness.Furthermore, a very considerable saving A test for ductility may be madeby plating on in time and in cost on the production of plated anon-adherent surface and stripping off the foil 45 articles becomespossible, whether with nickel and bending it double on itself. A plate.001" plate per se or with additional chromium finish. thick which willpass this test without breaking Various so-called addition agents havebeen is considered to have good ductility. A plate proposed from time totime for inclusion in nickel .0005 thick which will just pass this testis conplating baths in order to control or affect the sidered to havepassable ductility, Aplate .0002" 50 character of the electrolyticallydeposited metal. thick which will not pass this test without break- Oneprincipal objective in such modification of ing is considered to havepoor ductility. the plating bath has been to increase the bright- Theaddition agents of the present invention ness or luster of the depositedmetal. not only produce plates with the highest order as Many of theseprevious nickel plating addition of brightness, but also with a highorder of ducagents have allowed a much heavier deposit of tility asdefined by the above scale. This is desirable and essential to thepractical use of bright nickel plating.

The principal object of the present invention, therefore, broadlystated, is to provide an improved process of and materials for use inthe process of electrodepositing nickel which will not only render thenickel plate desirably bright but 1 which will also preserve or renderthe plate desirably ductile.

Other objects of our invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention,then, consists of the means hereinafter more particularly pointed out inthe claims, the following description setting forth in detail certainapproved modes of operation of our process and combination ofingredients embodying ouninvention, such disclosure constituting,however, but certain of various forms in which the principles of ourinvention may be used.

Broadly stated, our invention comprises the discovery that by the use inacid nickel electrolytes of a plurality of addition agents respectivelyselected from certain different classes of compounds, we are able toproduce deposits which are superior to those obtainable by the use ofaddition agents from either one of such classes alone. We find that theaddition agents from one of said classes, although characterized by anembrittling tendency, are productive of extreme brightness when used incombination with addition agents from the other class and that additionagents from said other class not only cooperate in the production ofbrightness but also exert a ductilizing effect in the combination. Theuse of one addition agent from each class is preferable but a pluralityfrom each class can be used successfully. Our cooperating additionagents are suitable for use in a wide variety of nickel electroplatingsolutions. We have found them to be very effective in aqueous acidnickel sulfate solutions and aqueous acid nickel chloride solutions.Among the nickel sulfate solutions in which they are effective areaqueous acid solutions of nickel sulfate, nickel sulfate and nickelchloride, nickel sulfate and sodium chloride, nickel sulfate andhydrochloric acid, nickel sulfate and ammonium chloride, nickel sulfateand alkali metal chlorides other than sodium chloride, the chloridesserving to produce good anode corrosion. Our addition agents areeffective in nickel chloride solutions with and without nickel sulfate.In each of said solutions it is desirable, although not necessary, toemploy boric acid or another suitable bufiering agent. We may employsoluble or insoluble anodes. We prefer to employ a bath containingnickel sulfate together with a suitable chloride, preferably nickelchloride and a suitable buffer, preferably boric acid. We prefer toemploy one or more addition agents from one of said classes in quantityto produce the desired brightness and one or more from the other classin quantity to overcome to a substantial extent the resultingembrittling tendency.

As representative of separate classes of compounds which, when used incombination as above stated, produce improved results, are those classesof compounds which may be respectively identified as (l) the amino polyaryl methane compounds in which at least one amino group isconnected toan aryl group; and (2) the benzene sulfonamides, benzene sulfimides andsubstitution products of such compounds. Since these classes ofcompounds are in themselves distinct, it is believed advisable to dealwith them separately in more specifically identifying them and inpointing out specific examples which will be found to be particularlysuitable for use.

Amino compounds While this class of compounds has been identifled aboveas the amino aryl methanes, nevertheless, our invention contemplates foruse as this group of addition agents compounds characterized by thepresence of the primary, secondary or tertiary amino group, a largecyclic molecule and the dominance of the amino group or groups overother antagonistic groups.

A representative class of the above identified amino compounds are theamino substituted poly aryl methanes. nets of the poly aryl methaneswhich are within the contemplation of the invention may be classified asfollows, viz.:

The various substitution prod-- 1. Amino compounds with at least onealkyl sub- I stituent group.

2. Amino compounds with at least one aryl substituent group on one ofsaid aryl groups.

3. Amino compounds with at least one alkyl and at least one arylsubstituent group on one of said aryl groups.

4. Amino compounds with at least one hydroxyl group.

5. Amino compounds with at least one sulphonic group.

The alkyl groups may be present in certain of the above classes ofcompounds include methyl,

ethyl, etc. The additional aryl groups which may characterize certain ofthe above mentioned subclasses of compounds are the benzyl, phenyl,tolyl, etc.

The salts of the above referred to types of com- TABLE ITriphenylmethane derivatives 1. p.p'-Diamino-m-methyl fuchsonimoniumchloride (Fuchsin). Triaminotolyl diphenyl methane hydrochloride(reduction product of Fuchsin). Triaminotolyl phenyl carbitolhydrochloride (carbitol product of Fuchsin). Mixture of reductionproducts and carbitol of Fuchsin prepared as hereinafter explained.Symmetric tetramethyl-p-aminofuchsonimonium chloride (Malachite Green).6. Symmetric diethyl-di-p-sulfobenzyl-p-aminofuchsonimonium (sodium saltof internal sulfonate, Pontacyl Green B).

U PMN '7. Pentamethyltriaminotriphenyl methane acetate-(reductionproduct of Methyl Violet). 8. Pentamethyl p' p diaminofuchsonimoniumchloride (Gentian Violet). 9. Hexamethyl-p.p' diaminofuchsonimoniumchloride (Crystal Violet).

Diphenylmethane derivatives 10. 2.2,4.4',-tetramino 5.5 dimethyldiphenyl methane-sulphate.

11. Tetramethyldiaminobenzophertonimium chlorhydrate (Auramine 12.Tetramethyl diamino diphenyl methane hydrochloride.

It will be observed that all of the specific examples oftriphenylmethane derivatives given above are fuchsonimonium compounds,thus more specifically identifying a class of compounds which has beenfound to produce remarkably improved plates when employed as aconstituent in the bath comprising our invention.

We have found it most practical to prepare specific Example 4 givenabove in the following way: Fifty parts of the dye, 1,000 parts ofwater, 100 parts of granular nickel and 100 parts of hydrochloric acidare heated and mechanically stirred until the magenta color of fuchsinhas practically disappeared. The mixture is then stirred with a smallamount of activated carbon and filtered. The filtrate is made up to oneliter and contains the equivalent of five grams of the original fuchsinper 100 cc.

While the quantity of these substances employed is not sharply critical,they are used in small amounts, that is, amounts on the order of 2 to100 milligrams per liter of the bath. The upper limit being determinedby their embrittling effect and in some cases, their solubility.

Most of the specific examples given in Table I are commercial products.There are many other members of the same groups, mostly not commercialproducts or not obtainable in pure form, which we believe would, ifavailable and sufficiently pure, have the same effect. In general,impurities are undesirable. Fuchsin and its carbitol and reductionproducts, prepared as above indicated and 2.2',4.4'-tetramino5.5-dimethyl diphenyl methane produce plate of outstanding quality ascompared with any of the other compounds listed. The presence of theprimary, secondary or tertiary amino group, the large cyclic moleculeand the dominance of the amino group or groups over any antagonisticgroups are believed to be the significant factors which account for theimproved results.

The benzene sulfonamides and substituted benzene sulfonamides The secondclass of materials, representative specific examples of which areemployed in combination with one or more specific examples of the firstclass of compounds above identified, i. e., the amino compounds, may be,as indicated, chemically identified as aryl sulfonamides, arylsulfimides, and substitution products thereof.

Particular examples are:

TABLE I1 UIPOONJ With the above listed brightening agents, this group,which for convenience may be termed a sulfonamide group, even though oneof the amino hydrogens has been replaced, appears to be, in the ease ofthe single aryl ring compounds, superior to the sulfonate group. In thecase of naphthalene compounds, the sulfonate group appears to besuperior to the sulfonamide group.

The above-named addition agents of this sec- 0nd class may be used invarious quantities preferably upwards from V gram per liter, however, 5grams per liter or less is usually a sufiicient concentration for bestresults. Larger quantities, within the limits of solubility. do no harm.

A conventional acid nickel bath in which the combined use of the twoclasses of addition agents will be found to give improved results, asabove indicated. consists of NiSO4'6H2o** 120-450 grams per literNiCl-GHzO 15-75 grams per liter HaBOa 15 grams per liter to saturationSodium lauryl sulfate* 0-1.0 gram per liter Current density Up to 60amperes per sq. ft.

Temperature Room-170 F.

*Where this compound is referred to, the material sold under the tradename of Duponol M, E. Dry is to be understood. It is sold as thetechnical compound. Other equivalent surface tension reducing agents mabe used instead of Duponol. Preparations known as ergltol 4 and Tergltol08, sold by Carbide & Carbon Chemicals Co. and said to be sodiumsecondary alcohol sulfates, may be used instead of Duponol. Thequantities required are of the same order.

"Some heptahydrate is usually present. Where nickel sulfate is usedherein in specific examples, this mixture of hydrates is to beunderstood.

In the above table giving the composition of a conventional bath, sodiumlauryl sulfate is added for the purpose of reducing the surface tensionof the bath to below 50 dynes per cm., in order to prevent pitting ofthe plate. Our invention contemplates the use of any surfacetension-reducing agent effective to reduce the surface tension of thebath to below 50 dynes per cm. The sulfates of normal primary aliphaticalcohols, having at least six carbon atoms, are a class of compoundssuitable for use for this purpose.

PARTICULAR EXAMPLES Example No. 1

Nickel sulfate grams per liter 240 Nickel chloride do 37.5 Boric acid"do--- 37.5 2.2, 4.4tetramino-5.5-dimethyl diphenyl-methane sulfategrams per liter 0.010 o-Benzoic sulfimide (saccharin) (sodium' salt)grams per Men. 1.0 Sodium lauryl sulfate (technicallfldon- 0.25 pH 3-4.5Temperature C 45-55 Current density amp./sq. ft 30-40 Example No. 2

Nickel sulfate grams per liter" 240 Nickel chloride do 37.5 Boric aciddo 37.5 Reduced fuehsin do *0.025 Benzene sulfonamide do 4.0 Sodiumlauryl sulfate (technical) -do 0.25 pH 3.0 Temperature C 50-55 Currentdensity amp./sq. ft" 40 That is, the reduction product of .025 g. of theunreduced dye.

Esample No. 3'

Nickel sulfate ..grams per liter 240 Nickel chlori'de do 37.5 Boric aciddo- 37.5 Reduced i'uchsin--. "do--- 0.005 Benzene sulfohydroxamic aciddo 2.0 pH 3.5 Temperature C 45-50 Current density-- amp./sq. ft 40 Thatis, the reduction product of .005 g. oi. the unreduced dye. I

Example No. 4 Nickel sulfate grams per liter 24o Nickel chloride do 37.5Boric acid do 37.5 Reduced fuchsin do 0.005 p-Toluene sulfonamide do 1.0DH; 4.0 Temperatureu n, C -55 Current density amp./sq. ft 40 That is,the reduction product of .005 g. of the unreduced dye.

Example No. 5

Nickel sulfate grams per liter" 240 Nickel chloride do 37.5 Boric aciddo 37.5 Reduced fuchsin ;do 0.005 o-Toluene sulionamide do 1.0 'pH 4.0Temperature C 50-55 Current density amp./sq. ft 40 That is, thereduction product of .005 g. of the unreduced dye.

Example No. 6

Nickel sulfate grams per Men. 240 Nickel chloride do 37 .5 Boric acid do37.5 Fuchsin do 0.015 o-Benzoic suiflmide do 3.0 Sodium lauryl sulfate(technical) do 0.25 pH 3.0 Temperature C -60 Current density amp./sq.i't

This application is a continuation-in-part of Lind et 9.1., application,Ser. No. 200,121, filed April 5, 1938, which is now abandoned.

Having thus described our invention, what we claim is:

1. An electroplating solution comprising an aqueous, acid solution of anickel electrolyte oi. the class consisting of nickel sulfate and nickelchloride, said solution having the capability of producing bright andductile deposits of nickel, such capability having been imparted theretoby the inclusion therein of cooperating addition agents, one of saidaddition agents being an 'amino poly aryl methane compound in which atleast one amino group is attached to an aryl group and the other of saidaddition agents being a substance of the class consisting of single ringaryl sulfonamides and sulfimides.

2. An electroplating solution comprising an aqueous, acid nickel sulfatesolution having the capability of producing bright and ductile depositsof nickel, such capability having been imparted thereto by the inclusiontherein of co-- operating addition agents, one of said addition agentsbeing an amino poly aryl methane compound in which at least one aminogroup is attached to an aryl group and the other of said addition agentsbeing a substance of the class consisting of single ring arylsulfonamides and sulamazes capability having been imparted thereto bythe inclusion therein of one or more substances of the class consistingof nickel chloride, ammonium chloride, hydrochloric acid and alkalimetal chlorides, said solution also containing boric acid.

5. An electrodeposition bath comprising an aqueous acid solutioncontaining nickel sulfate, nickel chloride and cooperating additionagents, one of said addition agents being an amino poly aryl methanecompound in which at least one amino group is connected to an arylgroup, soluble in the bath to the extent of at least two milligrams perliter and characterized by a brightening and embrittling tendency, andthe other of said addition agents being a substance of the classconsisting of single ring aryl sulfonamides and sulfimides soluble inthe bath to the extent of at least gram per liter.

6. An electrodeposition bath comprising an aqueous acid solutioncontaining nickel sulfate, nickel chloride and cooperating additionagents of two classes, one of said classes consisting of carbitol offuchsin, fuchsin, reduced fuchsin, 2.2, 4.4'-tetramino5.5'-dimethyl-diphenyl methane, and the chlorides, hydrochlorides,acetates and sulfates thereof and the other of said classes consistingof single ring aryl sulfonamides and sulfimides soluble in the bath tothe extent of at least V gram per liter.

7. An electrodeposition bath as defined in claim 5 further characterizedin that the first mentioned addition agent ispresent in the bath inquantity from 2 to 100 milligrams per liter and the second mentionedaddition agent is present in quantity sufiicient to render the depositductile. I

8. An electrodeposition bath as defined in claim 6 further characterizedin that the first mentioned addition agent is present in solution inquantity from 2 to 100 milligrams per liter and the second mentionedaddition agent is present in solution in quantity from gram per lite tosaturation.

9. An electrodeposition bath as defined in claim 6 further'characterizedin that the first mentioned addition agent is present in the bath inquantity from- 2 to 10 milligrams per liter and the second mentionedaddition agent is present in quantity from /2 gram to 5 grams per liter.

10. An electrodeposition bath comprising an aqueous acid solutioncontaining nickel sulfate, nickel chloride and cooperating additionagents effective to produce bright and ductile deposits, one of saidaddition agents being an amino poly aryl methane compound in which atleast one amino group is connected to an aryl group, soluble inthe bathto the extent of at least two milligrams per liter and characterized byabrightens ing and embrittling tendency, the other of said additionagents being a substance of the class consisting of single ring arylsulfonamides and sulfimides soluble in the bath to the extent of atleast gram per liter.

11. An electrodeposition bath as recited in claim 5 wherein the secondmentioned addition agent is saccharine.

12. An electrodeposition bath as recited in claim 6 wherein said secondmentioned addition agent is saccharine.

13. An electrodeposition bath as recited in claim 10 wherein said secondmentioned addition agent is saccharine.

14. An electrodeposition bath as recited in claim 6 wherein said firstmentioned addition agent is reduced fuchsin employed in quantity from 2to 100 milligrams per liter and said second mentioned addition agent issaccharine employed in quantity from gram per liter to saturation.

15. An electrodeposition bath as recited in claim 6 wherein said firstmentioned addition agent is reduced iuchsin employed in quantity from 2to 10 milligrams per liter and said second mentioned addition agent issaccharine employed in quantity from gram to 5 grams per liter.

16. An electrodeposition bath as recited in claim 6 wherein said firstmentioned addition agent is Iuchsin employed in quantity from 2 to 100milligrams per liter and said second men tioned addition agent issaccharine employed in quantity from gram per liter to saturation.

1'7. An electrodeposition bath as recited in claim 6 wherein said firstmentioned addition agent is carbitol of fuchsin employed in quantityfrom 2 to 100 milligrams per liter and said second mentioned additionagent is saccharine employed in. quantity from gram per liter tosaturation.

18. An electrodeposition bath comprising an aqueous acid solution ofnickel sulfate, nickel chloride, boric acid and cooperating additionagents effective to produce bright and ductile deposits, one of saidaddition agents being an amino poly aryl methane compound in which atleast one amino group is connected to an aryl group, soluble in the bathto the extent of at least two milligrams per liter and characterized bya brightening and embrittling tendency, the other of said additionagents being a substance of the class consisting of single ring arylsulfonamides and sulfimides soluble in the bath to the extent of atleast gram per liter.

RUDOLF LIND. WILLIAM J. HARSHAW. KENNETH E. LONG.

